Saturday, March 29, 2008

Instruction manual for Commtel COM203 scanner (Also Realistic PRO-39)

This is my own home written manual for the Commtel COM203 scanner which was sold around 1993/94.
This manual assumes you already know how to use volume and squekch controls, install batteries etc.

The scanner is marked on the back "Commtel COM203, made in China for Commtel by GRE".
The COM203 is identical to the Realistic or Radio Shack PRO-39 and made by the same company (GRE), although the band coverage may vary (see coverage below).The later COM204 and PRO-43 models have the same operating controls but different frequency bands and the ability to switch between AM and FM on any band at will (the COM203 uses FM on all frequencies apart from airband where it switches to AM).

Its not a particularly sensitive scanner. On airband my cheap Maycom 108 scanner is much more sensitive.The Commtel also suffers from breakthrough on airband from strong local amateur radio transmissions on 144 MHz.On the plus side, the Commtel and Realistic scanners are very cheap second hand, the batteries last a long time and they can stand a lot of abuse.My Commtel also has a matching carying case which gives it some protection against light rain.

Coverage and model variations
68-88 MHz (US version has 30-54 MHz instead)
108-174 MHz (Switches automatically to AM on airband frequencies)
380-512 MHz
806-960 MHz (US version has gaps from 824-851 MHz and 869-896 MHz to prevent access to analogue cellular frequencies)

It is possible to modify the coverage by adjusting jumper diodes.
This can enable the blocked cellular freqencies or swap the 68-88 MHz for 30-54 MHz and visa versa.
If you have the skills you might be able to add a switch to allow coverage of both 30-54 MHz and 68-88 MHz by switching the jumper diodes over.
There are modifications and jumper information available elsewhere on the internet:

The scanner has 10 banks of 20 channels where frequencies can be stored.200 memories in total, plus 10 Monitor frequencies which act as temporary memories when looking for new signals.Normally the scanner will scan all 10 banks of memories, but when it is scanning you can press the buttons on the front to remove any of the banks from the can process.
This is why the buttons are marked "1-20", "21-40" etc.
The scanner can scan up to 25 memory channels per second.

Programming the memory channels
Key in the memory number you want to use
Press PGM (PGM will light up on the display)
Enter a frequency (using the number decimal point keys)
Press ENTER to store the frequency in the chosen memory.

Repeat this process until you have programmed in all your chosen memories.

Scanning the memories
To start scanning the 200 memory channels press SCAN.
Pressing DELAY will cause the scanner to pause for 2 seconds at the end of each transmission so it does not start scanning and miss the other side of the conversation (DLY will be shown in thew display).
If the scanner stops on a signal you do not want to listen to press SCAN to continue the scan.
To stop scanning press MANUAL.

If a channel is constantly causing the scanner to stop you can remove it from the scan by pressing L/OUT when the scanner stops on it.
This will remove it from the scan.To put that memory back into the scan you need to select the channel manually and then press the L/OUT button again.
You can remove any block of 20 memory channels from the scan by pressing on the appropriate button.
You will see a bar in the display under the blocks you are currently scanning.
This allows you to have all your aircraft frequencies in one block and all your amateur radio frequencies in another so you can scan one without the other.

Selecting memory channels manually
Key in the number of the memory channel you want to listen to and press MANUAL
To move through the memory channels keep pressing MANUAL and the scanner will switch through the 200 memory channels one at a time.

Scanning using the limit function
Press PGM
Enter the lowest frequency you want to scan from
Enter the highest frequency you want to scan to
Press the up arrow and the scanner will start to scan from the lowest frequency set.
The scanner will stop on a transmission.
If you want to keep a note of this frequency you can store it in the current temporary monitor memories by pressing the MON button.
If you have stored a frequency in the monitor memory you can return to the limit search by pressing LIMIT followed by the up or down arrow.

Manual Tuning
Press MANUAL followed by MON then use the up and down arrow buttons to scan up or down from that frequency.
"-d-" is shown in the display to denote that you are not on any stored channel.
You can also scan up or down manually from any one of the 200 memory channels.
If you want to keep a note of this frequency you can store it in the current temporary monitor memories by pressing the MON button.

Using the Monitor channels
To listen to the memorised monitor channels press MANUAL then MON and then the number of the monitor memory you want to listen to.
The monitor channel you are listening to is indicated by the bar under the memory number in the display.
You can move stored frequencies from one of the temporary monitor memories to one of the permanent 200 memory channels like this:
Enter the channel number you want to move the monitor memory frequency to.
Press PGM
Press MON
Select the correct monitor memory

Priority Channel
To program the priority channel do this:
Press PGM
Enter the channel number you want to use as the priority one.
Press PRI
P appears in the display whenever you are on the priority channel.

To turn on the priority channel function press PRI (PRI will appear in the display).
The priority channel will be checked every two seconds and the scanner will switch to it if a signal is present.
To turn off the priority function press PRI again.

(c) 2008 Gordon Hudson, GM4SVM